August 10, 1900.] 



SCIENCE. 



229 



ber of karyosomes, which later become chrom- 

 omeres. There are twenty four of these in 

 the spermatocytes and forty-eight in the sperm- 

 atogonia. The spireme consists of a single 

 linin thread connecting these chromomeres and 

 forming a spiral which winds about the nucleus 

 just beneath the nuclear membrane. At this 

 stage the nucleus is an ellipsoid of revolution. 

 The spireme makes three complete whorls 

 about the spermatocyte nucleus ; but six 

 such whorls are formed in the nucleus of the 

 spermatogonium. The centrosome appears at 

 one side of the nucleus in the plane of its 

 minor axis. The nucleus changes next to an 

 oblate spheroid with the centrosome over the 

 pole. The arcs of the spiremes form merid- 

 ians. There are, therefore, six such meridians 

 in the spermatocytes and twelve in the sperm- 

 atogonia. Each has four chromomeres. The 

 spireme now divides at the poles into six and 

 twelve segments respectively. These contract, 

 forming spherical chromosomes at the equater. 

 In the chromosomes the individual chrom- 

 omeres are indistinguishable. Twenty-four 

 karyosomes are to be made out in the late met- 

 aphase of the spermatogonic divisions. 



The spermatid nucleus assumes the ellipsoid 

 shape. The cytoplasm immediately about it 

 changes so that it will not stain and a small 

 drop of non-staining material forms at one end 

 of the nucleus. This grows in size as the cyto- 

 plasm appears to be altered by the nucleus, 

 absorbed by it and stored. This droplet in- 

 creases until the nuclear wall which covers it, 

 touches and fuses with the cell wall. A slight 

 projection appears at this point of fusion. It 

 rapidly elongates to make the tail. The drop- 

 let which forms the middle piece decreases cor- 

 respondingly. Meantime the cytoplasm and 

 cell wall have completely disappeared. The 

 centrosome appears within the middle piece. 

 From it anteriorly and posteriorly runs the 

 axial fibre. Within the head of the sperm six 

 dumbbell-shaped bodies are apparent, the per- 

 sistent chromosomes. 



The next meeting was held on May 29th and 

 was devoted to two papers. The first of these 

 ' Variation in Daphnia hyalina ' was read by 

 Miss M. M. Enteman. The following is a brief 

 abstract : 



The shell of D. hyalina is extremely variable. 

 For the head crest a range of variation is ob- 

 served covering forms characteristic for many 

 different species of the genus Daphnia. The 

 principal forms described for Europe are a low- 

 rounded and a high-rounded crest, and a crest 

 terminating in a more or less acuminate apex. 

 In America, the species, as far as studied, shows 

 the same variations, and, in addition, a triangu- 

 lar and an extremely recurved crest. Further 

 it is to be noted, that while the European varie- 

 ties resemble other European species in the 

 form of the shell, the American varieties re- 

 semble the American representatives of these 

 species. A study of local variation shows widely 

 differing conditions for related regions, some 

 lakes possessing a single stable form, while 

 others furnish all transitions between extreme 

 varieties. Finally, however, different the sum- 

 mer varieties, they are all represented by a 

 uniformly low-crested form in the winter. The 

 species abounds in our clear northern lakes, 

 and these considerations ought to make it a 

 favorable subject for the determination of en- 

 vironmental influences. 



The second paper of the session was a review 

 by Mr. R. H. Johnson of the paper ' On the 

 Reactions of Daphnia magna Strauss to Certain 

 Changes in its Environment ' by E. Warren 

 {Quart. Journ. Micr. ScL, Vol. XLIII., Pt. 2, 

 1900). 



C. M. Child. 



THE BOTANICAL CLUB OF CANADA. 



The Botanical Club of Canada was organized 

 by a committee of section four of the Royal 

 Society of Canada, at its meeting in Montreal, 

 May 29, 1891. The object is to promote by 

 concerted local efforts and otherwise the ex- 

 ploration of the flora of every portion of Brit- 

 ish America, to publish complete lists of the 

 same in local papers as the work goes on, to 

 have these lists collected and carefully exam- 

 ined in order to arrive at a correct knowledge 

 of the precise character of our flora and its 

 geographical distribution, and to carry on sys- 

 tematically seasonal observations on botanical 

 phenomena. The intention is to stimulate 

 with the least possible paraphernalia of consti- 

 tution or rules, increased activity among botan- 



